The present invention relates to the art of computer driven printers, particularly, large format color ink jet printers. Printers of this type have a printhead carriage which is mounted for reciprocal movement on the printer in a direction orthogonal to the direction of movement of the paper or other medium on which printing is to take place through the printer. The printer carriage of a color printer typically has four removable electric or thermal ink jet printheads mounted thereon. Each of the printheads contains a supply of ink which, for large scale printers, is generally inadequate due to the large volumes of ink which are required as compared with the ink supply requirements of desk top printers. Consequently, various means have been proposed for continuously or periodically refilling the carriage-borne printheads with ink. These systems fall into two categories. The first comprises offboard or off-axis ink reservoirs which are continuously connected to the carriage-borne or onboard printheads by flexible tubes. The second comprises a "take a gulp" system in which the printhead carriage is periodically moved to one end of its path of travel where it is then connected with off-axis ink reservoirs to fill the onboard printheads. This "take a gulp" system is disclosed in Hewlett-Packard's Designjet 2000 printer referred to in U.S. patent application Ser. No. 08/805,861 filed Mar. 3, 1997 and published in European Patent Publication No.0863016 on Sep. 9, 1998.
Large format printers are expensive pieces of equipment which preferably should be capable of using different types of ink without significant modification of the printer. The different ink types may for convenience be broadly referred to as indoor ink and outdoor ink, meaning ink intended to be used for production of drawings, posters, and other printed material which may be displayed outdoors or indoors. Outdoor ink is pigment based, i.e. containing a plurality of discrete undissolved pigment particles suspended in a fluid carrier. Dye-based ink has a lower degree of optical density and permanence but is less expensive. Since pigment based inks and dye-based inks are incompatible with each other, a system is desired which enables the use of either type of ink in a printer without cross-contamination of the printer inks by each other.
Further, in color printers four separate colors of ink are usually employed comprising black and three primary or mid-primary colors such as cyan, magenta and yellow. In color ink printers provision must also be made to ensure that neither incorrect types of ink nor incorrect colors of ink can inadvertently be used in the system.